Get Information with scan Format Strings
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The Section MH Format Strings
showed how to write format files for scan.
Format files, or format strings, are a great way to get information
about mail messages for a shell program.
For instance, here's a a format string that prints the message number
in a field of width 4, a space, then either the Sender:
(if the message has one) or the From:.
It formats the addresses with the %(friendly) function,
which gives a "nice" output when it can.
$ scan -format "%4(msg) %<{sender}%(friendly{sender})%|%(friendly{from})%>"
46 "Don C. Meach"
47 mh-users-request@ics.uci.edu
48 Jerry Peek
You could use a scan format string like that to write a
simple loop that processes mail messages automatically.
The loop below uses the (mbox) function to get the address without
the hostname.
(There are more efficient ways to process incoming
mail -- see the Chapter
Processing New Mail Automatically.)
msgfrom="%(msg) %<{sender}%(mbox{sender})%|%(mbox{from})%>"
...
scan -format "$msgfrom" |
while read msgnum from
do
# DON'T READ ANYTHING FROM steveq; refile ALL mh-users MAIL.
# LEAVE OTHER MESSAGES ALONE:
case "$from" in
steveq) rmm $msgnum ;;
mh-users) refile $msgnum +mh-users ;;
esac
done
This is using a Bourne shell while loop with its standard input
taken from the pipe (from the scan command).
The read command reads a line of input; it puts the first word
(here, the message number) in a shell variable named msgnum, and the
rest (the local part of the address) goes into the variable called from.
Then, a case structure checks who sent the message and does
the right thing with it.
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